I just took a look at Google Earth. The Puyallup Assembly sits on about 15 acres. I haven't been there in a long time, when I was going there I think it held 2500-3000 people.
A properly designed parking lot holds about 100 cars. A fifty acre parking lot would hold 5000 cars. That is a lot of people, easily 10,000. Are they holding conventions that large in these buildings?